Federal and state regulations often require persons working at elevated heights to utilize fall-arrest equipment. Fall-arrest equipment commonly includes a body harness for attaching to a user and a lanyard for connecting to an anchorage point. Often, the final connection to the anchorage point is made with a hook or a carabiner at the end of the lanyard. Although, regardless of the type of connection, the connector must be manufactured to meet American National Standards Institute (ANSI) and Occupational Safety and Health Administration (OSHA) standards for minimum strength requirements for the hook body, gate/latch and locking mechanism. Additionally, other standards may also apply, for example, depending on the connectors intended use.
Safety hooks typically include a hook body, release lever (also known as a lock lever) and a gate. Additionally, safety hooks typically include springs and fasteners that hold the body, gate and release lever together and in a locked position. The release lever or lock lever of a hook is arranged to shift the locking mechanism away from the gate to allow the gate to open. The gate of a hook is arranged to prevent the hook from disengaging from an anchorage point, while the locking mechanism prevents the gate from opening unintentionally.
Under ideal circumstances, when a person falls, the connector, e.g., the hook, hangs vertically and the force of the fall is absorbed along the principal axis of the hook body. However, anchorage points vary greatly from specifically engineered hardware, to structural elements in buildings and fabrications, to even tree limbs. Because of the wide range of anchorage situations, and the variety of positions a person may be in when they fall relative to the anchorage point, the hook may be prevented from moving to its ideal vertical hanging position. In such situations, forces from the fall may act against the gate/latch and/or locking mechanism, which in the majority of hooks are not as strong as the hook body. Component failure and personal injury are often results of such falls, thus the need for latching mechanisms that can withstand greater forces.
Current ANSI and OSHA standards require hooks and carabiners to be self-closing, self-locking and capable of being opened only by at least two consecutive deliberate actions. Proposed new ANSI standards, e.g., Z 359.1-07ED, significantly change specifications for fall-arrest hardware. The following table summarizes recent proposed changes to the aforementioned standard:
TABLE 1HardwareExistingProposedFeatureTest descriptionstandardStandardGate faceLoad test for strength of gate250 lbs3,600 lbsand locking mechanismGate sideLoad test for strength of gate in350 lbs3,600 lbsresisting side loads
Hook bodies are most commonly constructed of heat treated carbon steel, forged or stamped, while the gate and lock lever are often constructed of stamped mild steel. However, one of ordinary skill in the art will recognize that other materials may also be used depending upon the desired strength of the assembled hook. For example, safety hooks that do not need to meet the described ANSI test standards may have molded plastic bodies, gates or release levers. Most prior art hooks act on the principal that force applied to the gate and lock, i.e., gate face load, is resisted by the strength of the gate and lock lever material and the rivets or fasteners they pivot on. Depending on the configuration of the mechanism, the force applied against the gate face, and transferred to the lock, can be multiplied by the ‘lever nature’ of both the gate and the lock lever, so that 3,600 lbs can become 5,000+lbs. Due to the configuration of these mechanisms, much of this load is applied against the rivets or fasteners of the gate and lock lever.
Some gates of prior art hooks can withstand 3,600 lb gate side loads, while others can be easily modified to withstand these loads, by constructing existing gates out of thicker heat treated materials, however such modifications increase cost, size and/or weight of a hook. Contrarily, gates are not so easily modified to withstand face loads, i.e., loads applied to the face of the gate which transmit from the gate to the locking mechanism and lock lever and subsequently to the rivets or fasteners on which they pivot and are mounted to the body with. It is impractical or simply impossible to make all elements, of existing hook designs, bigger, thicker or of stronger materials to withstand such loads. Such issues present particularly difficult problems to overcome when modifying prior art hooks which have larger hook bodies, e.g., hook bodies having lengths of six inches or greater. Hooks of such size can not merely have gates and/or locking mechanisms increased in size and/or thickness because their sizes and thicknesses would make them impractical to manufacture and use.
An additional issue present with hooks of this size is caused by the increased lengths of the hooks, and therefore increased lever arm lengths, e.g., the distance between the point of pressure applied to a gate and the locking point, and the distance between the locking point and the pivot axis of the gate. In this instance, when an amount of force is applied to the gate, the locking point acts as a fulcrum, and an increased amount of force is imparted on the pivot axis of the gate. Similarly, an increased lever arm is created from the point of pressure applied to a gate and the pivot axis of the gate. In this instance, when an amount of force is applied to the gate, the gate pivot axis acts as a fulcrum, and an increased amount of force is imparted on the locking point and thereby to the pivot axis of the locking lever. As these pivot axes at typically manufactured from rivets, there is a limited amount of strength which can be built into the pivot axis. Thus, when higher loads are applied to gates on larger hooks, the pivot axes, e.g., rivets, often fail due to their limited strength.
As can be derived from the variety of devices and methods directed at providing strength at gate and locking lever pivot axes, many means have been contemplated to accomplish the desired end, i.e., axes which can withstand elevated forces. Heretofore, tradeoffs between hook/material sizes and material types were required. Thus, there is a long-felt need for a hook which can withstand elevated gate face load forces without pivot axis failure. There is a further long-felt need for a safety hooks capable of passing increasing safety standards. There is also yet another long-felt need for a safety hook having the foregoing characteristics which functions easily and is economical and simple to manufacture.